Wellbores are formed in subterranean formations for various purposes including, for example, extraction of oil and gas from the subterranean formations and extraction of geothermal heat from the subterranean formations. Wellbores can exhibit extremely aggressive environments. For example, wellbores can exhibit abrasive surfaces, can be filled with corrosive chemicals (e.g., caustic drilling muds; well fluids, such as salt water, crude oil, carbon dioxide, and hydrogen sulfide; etc.), and can exhibit increasing high temperatures and pressures at progressively “down-hole” locations. For example, bottom-hole temperatures and pressures at depths of from about 5,000 to about 8,000 meters are often greater than 250° C. and 150 megapascals (MPa), respectively.
The extremely aggressive environments of wellbores can rapidly degrade the materials of assemblies, tools, and structures used in various down-hole applications (e.g., drilling applications, conditioning applications, logging applications, measurement applications, monitoring applications, exploring applications, etc.). Such degradation limits operational efficiency, and results in undesirable repair and replacement costs. Accordingly, there is a continuing need for structures having material configurations capable of withstanding such extremely aggressive environments, as well as for methods of forming such structures.